<html>

<head>
<meta http-equiv="Content-Language" content="en-us">
<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Filesystem Tutorial</title>
<link href="styles.css" rel="stylesheet">
</head>

<body>

<table border="0" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111">
  <tr>
    <td width="277">
<a href="../../../index.htm">
<img src="../../../boost.png" alt="boost.png (6897 bytes)" align="middle" width="300" height="86" border="0"></a></td>
    <td align="middle">
    <font size="7">Filesystem Tutorial</font>
    </td>
  </tr>
</table>

<table border="0" cellpadding="5" cellspacing="0" style="border-collapse: collapse"
 bordercolor="#111111" bgcolor="#D7EEFF" width="100%">
  <tr>
    <td><a href="index.htm">Home</a> &nbsp;&nbsp;
    <a href="tutorial.html">Tutorial</a> &nbsp;&nbsp;
    <a href="reference.html">Reference</a> &nbsp;&nbsp;
    <a href="faq.htm">FAQ</a> &nbsp;&nbsp;
    <a href="release_history.html">Releases</a> &nbsp;&nbsp;
    <a href="portability_guide.htm">Portability</a> &nbsp;&nbsp;
    <a href="v4.html">V4</a> &nbsp;&nbsp;
    <a href="v3.html">V3 Intro</a> &nbsp;&nbsp;
    <a href="v3_design.html">V3 Design</a> &nbsp;&nbsp;
    <a href="deprecated.html">Deprecated</a> &nbsp;&nbsp;
    <a href="issue_reporting.html">Bug Reports </a>&nbsp;&nbsp;
    </td>
</table>

<p>
      <a href="#Introduction">Introduction</a><br>
      <a href="#Preliminaries">Preliminaries</a><br>
      <a href="#Reporting-size">Reporting the size of a file - (tut1.cpp)</a><br>
      <a href="#Using-status-queries">Using status queries to determine file existence and type - (tut2.cpp)</a><br>
      <a href="#Directory-iteration">Directory iteration plus catching
      exceptions - (tut3.cpp)</a><br>
      <a href="#Using-path-decomposition">Using path decomposition, plus sorting results - (tut4.cpp)</a><br>
      <a href="#Class-path-Constructors">Class path: Constructors, including
      Unicode - (tut5.cpp)</a><br>
      <a href="#Class-path-formats">Class path: Generic format vs. Native format</a><br>
      <a href="#Class path-iterators-etc">Class path: Iterators, observers, composition, decomposition, and query - (path_info.cpp)</a><br>
      <a href="#Error-reporting">Error reporting</a><br>
</p>
<h2><a name="Introduction">Introduction</a></h2>

<p>This tutorial develops a little command line program to list information
about files and directories - essentially a much simplified version of the POSIX <code>ls</code> or Windows <code>dir</code>
commands. We'll start with the simplest possible version and progress to more
complex functionality. Along the way we'll digress to cover topics you'll need
to know about to understand Boost.Filesystem.</p>

<p>Source code for each  of the tutorial programs is available, and you
are encouraged to compile, test, and experiment with it. To conserve space, we won't
always show boilerplate code here, but the provided source is complete and
ready to build.</p>

<h2><a name="Preliminaries">Preliminaries</a></h2>

<p>Install the Boost distribution if you haven't already done so. See the
<a href="http://www.boost.org/more/getting_started/index.html">Boost Getting
Started</a> docs.</p>

<p>This tutorial assumes you have bootstrapped Boost.Build and compiled Boost.Filesystem
as described in the Getting Started article. The <code>b2</code> executable is expected
to be available in <code>PATH</code>.</p>

<blockquote>

</blockquote>
<p>Fire up your command line interpreter, and type the following commands:</p>

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Ubuntu Linux</b></i></td>
    </tr>
    <tr>
      <td>
      <pre>$ cd <i><b>boost-root</b></i>/libs/filesystem/example

$ b2 tutorial
Compiling example programs...

$ ./tut1
Usage: tut1 path</pre>
      </td>
    </tr>
  </table>

  &nbsp;

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Microsoft Windows</b></i></td>
    </tr>
    <tr>
    <td>
      <pre>&gt;cd <i><b>boost-root</b></i>\libs\filesystem\example

&gt;b2.exe tutorial
Compiling example programs...

&gt;tut1
Usage: tut1 path</pre>
      </td>
    </tr>
  </table>

<p>If the <code>tut1</code> command outputs &quot;<code>Usage: tut1 path</code>&quot;, all
is well. The tutorial example programs are available in
<code><i><b>boost-root</b></i>/libs/filesystem/example</code>. Should you modify
and experiment with them as the tutorial progresses, just invoke <code>b2 tutorial</code> again
to rebuild.</p>

<p>If something didn't work right, here are some troubleshooting suggestions:</p>

  <ul>
    <li>If the <code>b2</code> program executable isn't being found, check your path environmental variable
    or see
    <a href="http://www.boost.org/more/getting_started/windows.html">Boost
    Getting Started</a>.<br>
&nbsp;</li>
    <li>Look at Boost bootstrap output to try to spot an indication of the
    problem.</li>
  </ul>

<h2><a name="Reporting-size">Reporting the size of a file</a> - (<a href="../example/tut1.cpp">tut1.cpp</a>)</h2>

<p>Let's get started. Our first example program, <a href="../example/tut1.cpp">tut1.cpp</a>,
reports the size of a file:</p>

<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
      <pre><!-- include file "../example/tut1.cpp" -->#include &lt;iostream&gt;
#include &lt;boost/filesystem.hpp&gt;
using namespace boost::filesystem;

int main(int argc, char* argv[])
{
  if (argc &lt; 2)
  {
    std::cout &lt;&lt; &quot;Usage: tut1 path\n&quot;;
    return 1;
  }
  std::cout &lt;&lt; argv[1] &lt;&lt; &quot; &quot; &lt;&lt; file_size(argv[1]) &lt;&lt; '\n';
  return 0;
}<!-- end include file --></pre>
    </td>
  </tr>
</table>

<p>The Boost.Filesystem <code><a href="reference.html#file_size">file_size</a></code>
function returns a <code>uintmax_t</code>
containing the size of the file named by the argument. The declaration looks
like this:</p>

<blockquote>
  <pre><code>uintmax_t file_size(const path&amp; p);</code> </pre>
</blockquote>
<p>For now, all you need to know is that <code>class path</code> has constructors that take
<code>const char *</code> and other string types. (If you can't wait to
find out more, skip ahead to the <a href="#Class-path-Constructors">class path</a> section of
the tutorial.)</p>
<p>Please take a minute to try out <code>tut1</code> on your system, using a
file that is known to exist, such as <code>tut1.cpp</code>. Here is what the
results look like on two different operating systems:</p>

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Ubuntu Linux</b></i></td>
    </tr>
    <tr>
      <td valign="top">
      <pre>$ ./tut1 tut1.cpp
tut1.cpp 569</pre>
      <pre>$ ls -l tut1.cpp
-rw-rw-r-- 1 beman beman 569 Jul 26 12:04 tut1.cpp</pre>
      </td>
    </tr>
  </table>

  &nbsp;

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Microsoft Windows</b></i></td>
    </tr>
    <tr>

      <td valign="top">
      <pre>&gt;tut1 tut1.cpp
tut1.cpp 592

&gt;dir tut1.cpp
...
07/26/2015 07:20 AM 592 tut1.cpp
...</pre>
      </td>
    </tr>
  </table>

<p>So far, so good. The reported Linux and Windows sizes are different because
the Linux tests used <code>&quot;\n&quot;</code> line endings, while the Windows tests
used <code>&quot;\r\n&quot;</code> line endings. The sizes reported may differ
from the above if changes have been made to <code>tut1.cpp</code>.</p>
  <p>Now try again, but give a path that doesn't exist:</p>

  <table border="1" cellpadding="5" cellspacing="0"
    style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Ubuntu Linux</b></i></td>
    </tr>
    <tr>
      <td valign="top">
      <pre>$ ./tut1 foo
terminate called after throwing an instance of &#39;boost::filesystem::filesystem_error&#39;
what(): boost::filesystem::file_size: No such file or directory: &quot;foo&quot;
Aborted (core dumped)</pre>
      </td>
    </tr>
  </table>

&nbsp;

  <table border="1" cellpadding="5" cellspacing="0"
    style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Microsoft Windows</b></i></td>
    </tr>
    <tr>
      <td valign="top">
      <pre>&gt;tut1 foo</pre>
      <p><b><i>An exception is thrown;<br>
      the exact form of the response depends on
      Windows system options.</i></b></td>
    </tr>
  </table>

  <p>What happens?
  There's no file named <code>foo</code> in the current directory, so by default an
exception is thrown. See <a href="#Error-reporting">Error reporting</a> to learn
  about error reporting via error codes rather than exceptions.</p>
  <p>Try this:</p>

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Ubuntu Linux</b></i></td>
    </tr>
    <tr>
      <td>
      <pre>$ ./tut1 .
terminate called after throwing an instance of &#39;boost::filesystem::filesystem_error&#39;
what(): boost::filesystem::file_size: Operation not permitted: &quot;.&quot;
Aborted (core dumped)</pre>
      </td>
    </tr>
  </table>

  &nbsp;

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Microsoft Windows</b></i></td>
    </tr>
    <tr>
      <td valign="top">
      <pre>&gt;tut1 .</pre>
      <p><b><i>An exception is thrown;<br>
      the exact form of the response depends on Windows system options.</i></b></td>
    </tr>
  </table>

  <p>The current directory exists, but <code>file_size()</code> works on regular
  files, not directories, so again an exception is thrown.</p>

  <p>We'll deal with those situations in <code>tut2.cpp</code>.</p>

<h2><a name="Using-status-queries">Using status queries to determine file existence and type</a> - (<a href="../example/tut2.cpp">tut2.cpp</a>)</h2>

<p>Boost.Filesystem includes status query functions such as <code>
<a href="reference.html#exists-path">exists</a></code>,
<code><a href="reference.html#is_directory-path">is_directory</a></code>, and <code>
<a href="reference.html#is_regular_file-path">is_regular_file</a></code>. These return
<code>bool</code>'s, and will return <code>true</code> if the condition
described by their name is met. Otherwise they return <code>false</code>,
including when any element
of the path argument can't be found.</p>

<p><a href="../example/tut2.cpp">tut2.cpp</a> uses several of the status query functions to cope with non-existent
files and with different kinds of files:</p>

<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
      <pre><!-- include file "../example/tut2.cpp" -->#include &lt;iostream&gt;
#include &lt;boost/filesystem.hpp&gt;
using namespace std;
using namespace boost::filesystem;

int main(int argc, char* argv[])
{
  if (argc &lt; 2)
  {
    cout &lt;&lt; &quot;Usage: tut2 path\n&quot;;
    return 1;
  }

  path p(argv[1]);  // avoid repeated path construction below

  if (exists(p))    // does path p actually exist?
  {
    if (is_regular_file(p))        // is path p a regular file?
      cout &lt;&lt; p &lt;&lt; &quot; size is &quot; &lt;&lt; file_size(p) &lt;&lt; '\n';

    else if (is_directory(p))      // is path p a directory?
      cout &lt;&lt; p &lt;&lt; &quot; is a directory\n&quot;;

    else
      cout &lt;&lt; p &lt;&lt; &quot; exists, but is not a regular file or directory\n&quot;;
  }
  else
    cout &lt;&lt; p &lt;&lt; &quot; does not exist\n&quot;;

  return 0;
}<!-- end include file --></pre>
    </td>
  </tr>
</table>

<p>Give it a try:</p>

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Ubuntu Linux</b></i></td>
    </tr>
    <tr>
      <td valign="top">
      <pre>$ ./tut2 tut2.cpp
&quot;tut2.cpp&quot; size is 997

$ ./tut2 foo
&quot;foo&quot; does not exist

$ ./tut2 .
&quot;.&quot; is a directory</pre>
      </td>
    </tr>
  </table>

&nbsp;

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Microsoft Windows</b></i></td>
    </tr>
    <tr>
       <td valign="top">
      <pre>&gt;tut2 tut2.cpp
tut2.cpp size is 1039

&gt;tut2 foo
&quot;foo&quot; does not exist

&gt;tut2 .
&quot;.&quot; is a directory</pre>
      </td>
    </tr>
  </table>

<p>Although tut2 works OK in these tests, the output is less than satisfactory
for a directory. We'd typically like to see a list of the directory's contents. In <code>tut3.cpp</code>
we will see how to iterate over directories.</p>

<p>But first, let's try one more test:</p>

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Ubuntu Linux</b></i></td>
    </tr>
    <tr>
      <td valign="top">
      <pre>$ ls /home/jane/foo
ls: cannot access /home/jane/foo: No such file or directory

$ ./tut2 /home/jane/foo
terminate called after throwing an instance of 'boost::
filesystem::filesystem_error&gt;'
   what(): boost::filesystem::status: Permission denied:
     &quot;/home/jane/foo&quot;
Aborted</pre>
      </td>
     </tr>
  </table>

  &nbsp;

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Microsoft Windows</b></i></td>
    </tr>
    <tr>
      <td valign="top">
      <pre>&gt;dir e:\
The device is not ready.

&gt;tut2 e:\</pre>
      <p dir="ltr"><b><i>An exception is thrown;<br>
      the exact form of the response depends on
      Windows system options.</i></b></td>
    </tr>
  </table>

<p>On the Linux system, the test was being run from an account that did not have
permission to access <code>/home/jane/foo</code>. On the Windows system, <code>
e:</code> was a Compact Disc reader/writer that was not ready. End users
shouldn't have to interpret cryptic exceptions reports, so as we move on to <code>tut3.cpp</code>
we will increase the robustness of the code, too.</p>

<h2><a name="Directory-iteration">Directory iteration</a> plus catching
exceptions - (<a href="../example/tut3.cpp">tut3.cpp</a>)</h2>

<p>Boost.Filesystem's <code><a href="reference.html#directory_iterator">
directory_iterator</a></code> class is just what we need here. It follows the
general pattern of the standard library's <code>istream_iterator</code>. Constructed from
a path, it iterates over the contents of the directory. A default constructed <code>directory_iterator</code>
acts as the end iterator.</p>

<p>The value type of <code>directory_iterator</code> is <code>
<a href="reference.html#directory_entry">directory_entry</a></code>. A <code>
directory_entry</code> object contains <code>path</code> and <code><a href="reference.html#file_status">file_status</a></code>
information. A <code>directory_entry</code> object
can be used directly, but can also be passed to <code>path</code> arguments in function calls.</p>

<p>The other need is increased robustness in the face of the many kinds of
errors that can affect file system operations. We could do that at the level of
each call to a Boost.Filesystem function (see <a href="#Error-reporting">Error
reporting</a>), but for simplicity <a href="../example/tut3.cpp">tut3.cpp</a>
uses an overall try/catch block.</p>

<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
      <pre><!-- include file "../example/tut3.cpp" -->#include &lt;iostream&gt;
#include &lt;boost/filesystem.hpp&gt;
using std::cout;
using namespace boost::filesystem;

int main(int argc, char* argv[])
{
  if (argc &lt; 2)
  {
    cout &lt;&lt; &quot;Usage: tut3 path\n&quot;;
    return 1;
  }

  path p (argv[1]);

  try
  {
    if (exists(p))
    {
      if (is_regular_file(p))
        cout &lt;&lt; p &lt;&lt; &quot; size is &quot; &lt;&lt; file_size(p) &lt;&lt; '\n';

      else if (is_directory(p))
      {
        cout &lt;&lt; p &lt;&lt; &quot; is a directory containing:\n&quot;;

        for (directory_entry&amp; x : directory_iterator(p))
          cout &lt;&lt; &quot;    &quot; &lt;&lt; x.path() &lt;&lt; '\n';
      }
      else
        cout &lt;&lt; p &lt;&lt; &quot; exists, but is not a regular file or directory\n&quot;;
    }
    else
      cout &lt;&lt; p &lt;&lt; &quot; does not exist\n&quot;;
  }

  catch (const filesystem_error&amp; ex)
  {
    cout &lt;&lt; ex.what() &lt;&lt; '\n';
  }

  return 0;
}<!-- end include file --></pre>
    </td>
  </tr>
</table>

<p>Give <code>tut3</code> a try, passing it a path to a directory as a command line argument.
Here is a run on a checkout of the Boost Git develop branch, followed by a repeat
of the test cases that caused exceptions on Linux and Windows:</p>

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Ubuntu Linux</b></i></td>
    </tr>
    <tr>
      <td valign="top">
      <pre>$ ./tut3 ~/boost/develop
    &quot;/home/beman/boost/develop&quot; is a directory containing:
    &quot;/home/beman/boost/develop/rst.css&quot;
    &quot;/home/beman/boost/develop/boost&quot;
    &quot;/home/beman/boost/develop/boost.png&quot;
    &quot;/home/beman/boost/develop/libs&quot;
    &quot;/home/beman/boost/develop/doc&quot;
    &quot;/home/beman/boost/develop/project-config.jam.2&quot;
    &quot;/home/beman/boost/develop/.gitmodules&quot;
    &quot;/home/beman/boost/develop/boostcpp.py&quot;
    &quot;/home/beman/boost/develop/.travis.yml&quot;
    &quot;/home/beman/boost/develop/.gitattributes&quot;
    &quot;/home/beman/boost/develop/index.htm&quot;
    &quot;/home/beman/boost/develop/index.html&quot;
    &quot;/home/beman/boost/develop/bjam&quot;
    &quot;/home/beman/boost/develop/project-config.jam.1&quot;
    &quot;/home/beman/boost/develop/LICENSE_1_0.txt&quot;
    &quot;/home/beman/boost/develop/.git&quot;
    &quot;/home/beman/boost/develop/tools&quot;
    &quot;/home/beman/boost/develop/stage&quot;
    &quot;/home/beman/boost/develop/boostcpp.jam&quot;
    &quot;/home/beman/boost/develop/Jamroot&quot;
    &quot;/home/beman/boost/develop/.gitignore&quot;
    &quot;/home/beman/boost/develop/INSTALL&quot;
    &quot;/home/beman/boost/develop/more&quot;
    &quot;/home/beman/boost/develop/bin.v2&quot;
    &quot;/home/beman/boost/develop/project-config.jam&quot;
    &quot;/home/beman/boost/develop/boost-build.jam&quot;
    &quot;/home/beman/boost/develop/bootstrap.bat&quot;
    &quot;/home/beman/boost/develop/bootstrap.sh&quot;
    &quot;/home/beman/boost/develop/status&quot;
    &quot;/home/beman/boost/develop/boost.css&quot;</pre>
    </td>
     </tr>
  </table>

  &nbsp;

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
       <td align="center"><i><b>Microsoft Windows</b></i></td>
    </tr>
    <tr>

      <td valign="top">
      <pre>&gt;tut3 \boost\develop
"\boost\develop" is a directory containing:
    "\boost\develop\.git"
    "\boost\develop\.gitattributes"
    "\boost\develop\.gitignore"
    "\boost\develop\.gitmodules"
    "\boost\develop\.travis.yml"
    "\boost\develop\bin.v2"
    "\boost\develop\boost"
    "\boost\develop\boost-build.jam"
    "\boost\develop\boost.css"
    "\boost\develop\boost.png"
    "\boost\develop\boostcpp.jam"
    "\boost\develop\boostcpp.py"
    "\boost\develop\bootstrap.bat"
    "\boost\develop\bootstrap.sh"
    "\boost\develop\doc"
    "\boost\develop\index.htm"
    "\boost\develop\index.html"
    "\boost\develop\INSTALL"
    "\boost\develop\Jamroot"
    "\boost\develop\libs"
    "\boost\develop\LICENSE_1_0.txt"
    "\boost\develop\more"
    "\boost\develop\project-config.jam"
    "\boost\develop\rst.css"
    "\boost\develop\stage"
    "\boost\develop\status"
    "\boost\develop\tools"</pre>
      <pre>&gt;tut3 e:\
boost::filesystem::status: The device is not ready: &quot;e:\&quot;</pre>
      </td>
    </tr>
  </table>

<p>Not bad, but we can make further improvements:</p>

    <ul>
      <li>The listing would be much easier to read if only the filename was
      displayed, rather than the full path.<br>
&nbsp;</li>
      <li>The Linux listing isn't sorted. That's because the ordering of
      directory iteration is unspecified. Ordering depends on the underlying
      operating system API and file system specifics. So we need to sort the
      results ourselves. </li>
    </ul>

<p>The next sections show how those changes play out, so read on!</p>

<h2><a name="Using-path-decomposition">Using path decomposition, plus sorting results</a> - (<a href="../example/tut4.cpp">tut4.cpp</a>)</h2>

<p>For directories, <a href="../example/tut4.cpp">tut4.cpp</a> builds a <code>
std::vector</code> of all the entries and then sorts it before writing to <code>
cout</code>.</p>

<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
    <pre><!-- include file "../example/tut4.cpp" -->#include &lt;iostream&gt;
#include &lt;vector&gt;
#include &lt;algorithm&gt;
#include &lt;boost/filesystem.hpp&gt;
using std::cout;
using namespace boost::filesystem;

int main(int argc, char* argv[])
{
  if (argc &lt; 2)
  {
    cout &lt;&lt; &quot;Usage: tut4 path\n&quot;;
    return 1;
  }

  path p (argv[1]);

  try
  {
    if (exists(p))
    {
      if (is_regular_file(p))
        cout &lt;&lt; p &lt;&lt; &quot; size is &quot; &lt;&lt; file_size(p) &lt;&lt; '\n';

      else if (is_directory(p))
      {
        cout &lt;&lt; p &lt;&lt; &quot; is a directory containing:\n&quot;;

        std::vector&lt;path&gt; v;

        for (auto&amp;&amp; x : directory_iterator(p))
          v.push_back(x.path());

        std::sort(v.begin(), v.end());

        for (auto&amp;&amp; x : v)
          cout &lt;&lt; &quot;    &quot; &lt;&lt; x.filename() &lt;&lt; '\n';
      }
      else
        cout &lt;&lt; p &lt;&lt; &quot; exists, but is not a regular file or directory\n&quot;;
    }
    else
      cout &lt;&lt; p &lt;&lt; &quot; does not exist\n&quot;;
  }

  catch (const filesystem_error&amp; ex)
  {
    cout &lt;&lt; ex.what() &lt;&lt; '\n';
  }

  return 0;
}<!-- end include file --></pre>
    </td>
  </tr>
</table>

    <p>The only difference between <code>tut3.cpp</code> and <code>tut4.cpp</code> is
    what happens for directories. We changed:</p>
    <blockquote>
      <pre>for (const directory_entry&amp; x : directory_iterator(p))
  cout &lt;&lt; &quot; &quot; &lt;&lt; x.path() &lt;&lt; &#39;\n&#39;;</pre>
    </blockquote>
    <p>to:</p>
    <blockquote>
      <pre>std::vector&lt;path&gt; v;

for (auto&amp;&amp; x : directory_iterator(p))
  v.push_back(x.path());

std::sort(v.begin(), v.end());

for (auto&amp;&amp; x : v)
  cout &lt;&lt; &quot; &quot; &lt;&lt; x.filename() &lt;&lt; &#39;\n&#39;;
</pre>
    </blockquote>
    <p> <code>
    <a href="reference.html#path-filename">filename()</a></code> is one of
    several class <code>path</code> decomposition functions. It extracts the
    filename portion
    from a path (i.e. <code>&quot;index.html&quot;</code>
    from <code>&quot;/home/beman/boost/trunk/index.html&quot;</code>). These decomposition functions are
    more fully explored in the <a href="#Class path-iterators-etc">Path iterators, observers,
    composition, decomposition and query</a> portion of this tutorial.</p>
    <p>The above was written as two lines of code for clarity. It could have
    been written more concisely as:</p>
    <blockquote>
      <pre>v.push_back(it-&gt;path().filename()); // we only care about the filename</pre>
    </blockquote>
    <p>Here is the output from a test of <code><a href="../example/tut4.cpp">tut4.cpp</a></code>:</p>

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Ubuntu Linux</b></i></td>
    </tr>
    <tr>
      <td>
      <pre>$ ./tut4 ~/boost/develop
"/home/beman/boost/develop" is a directory containing:
    ".git"
    ".gitattributes"
    ".gitignore"
    ".gitmodules"
    ".travis.yml"
    "INSTALL"
    "Jamroot"
    "LICENSE_1_0.txt"
    "bin.v2"
    "boost"
    "boost-build.jam"
    "boost.css"
    "boost.png"
    "boostcpp.jam"
    "boostcpp.py"
    "bootstrap.bat"
    "bootstrap.sh"
    "doc"
    "index.htm"
    "index.html"
    "libs"
    "more"
    "project-config.jam"
    "project-config.jam.1"
    "project-config.jam.2"
    "rst.css"
    "stage"
    "status"
    "tools"</pre>
      </td>
    </tr>
  </table>

&nbsp;

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Microsoft Windows</b></i></td>
    </tr>
    <tr>
      <td>
      <pre>&gt;tut4 \boost\develop
"\boost\develop" is a directory containing:
    ".git"
    ".gitattributes"
    ".gitignore"
    ".gitmodules"
    ".travis.yml"
    "INSTALL"
    "Jamroot"
    "LICENSE_1_0.txt"
    "bin.v2"
    "boost"
    "boost-build.jam"
    "boost.css"
    "boost.png"
    "boostcpp.jam"
    "boostcpp.py"
    "bootstrap.bat"
    "bootstrap.sh"
    "doc"
    "index.htm"
    "index.html"
    "libs"
    "more"
    "project-config.jam"
    "project-config.jam.1"
    "project-config.jam.2"
    "rst.css"
    "stage"
    "status"
    "tools"</pre>
      </td>
    </tr>
  </table>

    <p>That completes the main portion of this tutorial. If you haven't already
    worked through the <a href="#Class-path-Constructors">Class path</a> sections of this tutorial, dig into them now.
    The <a href="#Error-reporting">Error reporting</a> section may also be of
    interest, although it can be skipped unless you are deeply concerned about
    error handling issues.</p>

<h2><a name="Class-path-Constructors">Class path: Constructors</a>,
including Unicode - (<a href="../example/tut5.cpp">tut5.cpp</a>)</h2>

<p>Traditional C interfaces pass paths as <code>const char*</code> arguments.
C++ interfaces may add <code>const std::string&amp;</code> overloads, but adding
overloads becomes untenable if wide characters, containers, and iterator ranges
need to be supported.</p>
<p>Passing paths as <code>const path&amp;</code> arguments is far simpler, yet far
more flexible because class <code>path</code> itself is far more flexible:</p>
<ol>
  <li>Class <code>path</code> supports multiple character types and encodings, including Unicode, to
  ease internationalization.</li>
  <li>Class <code>path</code> supports multiple source types, such as iterators for null terminated
  sequences, iterator ranges, string class types (including <code>std::basic_string</code> and <code>std::basic_string_view</code>),
  and <code><a href="reference.html#Class-directory_entry">directory_entry</a></code>'s,
  so functions taking paths don't need to provide several overloads.</li>
  <li>Class <code>path</code> supports both native and generic pathname formats, so programs can be
  portable between operating systems yet use native formats where desirable.</li>
  <li>Class <code>path</code> supplies a full set of iterators, observers, composition,
  decomposition, and query functions, making pathname manipulations easy,
  convenient, reliable, and portable.</li>
</ol>
<p>Here is how (1) and (2) work. Class path constructors,
assignments, and appends have member templates for sources. For example, here
are the constructors that take sources:</p>

<blockquote>
  <pre>template &lt;class <a href="reference.html#Source">Source</a>&gt;
  path(Source const&amp; source);</pre>
  <pre>template &lt;class InputIterator&gt;
  path(InputIterator begin, InputIterator end);</pre>
</blockquote>
<p>Let's look at a little program that shows how comfortable class <code>path</code> is with
both narrow and wide characters in C-style strings, C++ strings, and via C++
iterators:</p>

<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
      <pre><!-- include file "../example/tut5.cpp" -->#include &lt;boost/filesystem/fstream.hpp&gt;
#include &lt;string&gt;
#include &lt;list&gt;
namespace fs = boost::filesystem;

int main()
{
  // \u263A is &quot;Unicode WHITE SMILING FACE = have a nice day!&quot;
  std::string narrow_string (&quot;smile2&quot;);
  std::wstring wide_string (L&quot;smile2\u263A&quot;);
  std::list&lt;char&gt; narrow_list;
  narrow_list.push_back('s');
  narrow_list.push_back('m');
  narrow_list.push_back('i');
  narrow_list.push_back('l');
  narrow_list.push_back('e');
  narrow_list.push_back('3');
  std::list&lt;wchar_t&gt; wide_list;
  wide_list.push_back(L's');
  wide_list.push_back(L'm');
  wide_list.push_back(L'i');
  wide_list.push_back(L'l');
  wide_list.push_back(L'e');
  wide_list.push_back(L'3');
  wide_list.push_back(L'\u263A');

  { fs::ofstream f(&quot;smile&quot;); }
  { fs::ofstream f(L&quot;smile\u263A&quot;); }
  { fs::ofstream f(narrow_string); }
  { fs::ofstream f(wide_string); }
  { fs::ofstream f(fs::path(narrow_list.begin(), narrow_list.end())); }
  { fs::ofstream f(fs::path(wide_list.begin(), wide_list.end())); }
  narrow_list.pop_back();
  narrow_list.push_back('4');
  wide_list.pop_back();
  wide_list.pop_back();
  wide_list.push_back(L'4');
  wide_list.push_back(L'\u263A');
  { fs::ofstream f(fs::path(narrow_list.begin(), narrow_list.end())); }
  { fs::ofstream f(fs::path(wide_list.begin(), wide_list.end())); }

  return 0;
}<!-- end include file --></pre>
    </td>
  </tr>
</table>

<p>Testing <code>tut5</code>:</p>

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Ubuntu Linux</b></i></td>
    </tr>
    <tr>
      <td valign="top">
      <pre>$ ./tut5

$ ls smile*
smile smile&#9786; smile2 smile2&#9786; smile3 smile3&#9786; smile4 smile4&#9786;</pre>
      </td>
    </tr>
  </table>

&nbsp;

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Microsoft Windows</b></i></td>
    </tr>
    <tr>
      <td valign="top">
      <pre>&gt;tut5

&gt;dir /b smile*
smile
smile2
smile2&#9786;
smile3
smile3&#9786;
smile4
smile4&#9786;
smile&#9786;</pre>
      </td>
    </tr>
  </table>

<p>The exact appearance of the smiling face will depend on the font,
font size, and other settings for your command line window. The above tests were
run with out-of-the-box Ubuntu 14.04 and Windows 7, US Edition. If you don't get
the above results, take a look at the <code><i><b>boost-root</b></i>/libs/filesystem/example</code>
directory with your system's GUI file browser, such as Linux Nautilus, Mac OS X
Finder, or Windows Explorer. These tend to be more comfortable with
international character sets than command line interpreters.</p>

  <p>Class <code>path</code> takes care of whatever character type or encoding
  conversions are required by the particular operating system. Thus as <code>
  tut5</code> demonstrates, it's no problem to pass a wide character string to a
  Boost.Filesystem operational function even if the underlying operating system
  uses narrow characters, and visa versa. And the same applies to user supplied
  functions that take <code>const path&amp;</code> arguments.</p>

  <p>Class <code>path</code> also provides path syntax that is portable across operating systems,
  element iterators, and observer, composition, decomposition, and query
  functions to manipulate the elements of a path. The next section of this
  tutorial deals with path syntax.</p>

<h2><a name="Class-path-formats">Class path: Generic format vs. Native format</a></h2>

<p>Class <code>path</code> deals with two different pathname
formats - generic format and native format. For POSIX-like
file systems, these formats are the same. But for users of Windows and
other non-POSIX file systems, the distinction is important. Even
programmers writing for POSIX-like systems need to understand the distinction if
they want their code to be portable to non-POSIX systems.</p>

<p>The <b>generic format</b> is the familiar <code>/my_directory/my_file.txt</code> format used by POSIX-like
operating systems such as the Unix variants, Linux, and Mac OS X. Windows also
recognizes the generic format, and it is the basis for the familiar Internet URL
format. The directory
separator character is always one or more slash characters.</p>

<p>The <b>native format</b> is the format as defined by the particular
operating system. For Windows, either the slash or the backslash can be used as
the directory separator character, so <code>/my_directory\my_file.txt</code>
would work fine. Of course, if you write that in a C++ string literal, it
becomes <code>&quot;/my_directory\\my_file.txt&quot;</code>.</p>

<p>If a drive specifier or a backslash appears
in a pathname on a Windows system, it is always treated as the native format.</p>

<p>Class <code>path</code> has observer functions that allow you to
obtain the string representation of a path object in either the native format
or the generic format. See the <a href="#Class path-iterators-etc">next section</a>
for how that plays out.</p>

  <p>The distinction between generic format and native format is important when
  communicating with native C-style API's and with users. Both tend to expect
  paths in the native format and may be confused by the generic format. The generic
  format is great, however, for writing portable programs that work regardless
  of operating system.</p>

  <p>The next section covers class <code>path</code> observers, composition,
  decomposition, query, and iteration over the elements of a path.</p>

<h2><a name="Class path-iterators-etc">Class path: Iterators, observers, composition, decomposition, and query</a>
- (<a href="../example/path_info.cpp">path_info.cpp</a>)</h2>

<p>The <code><a href="../example/path_info.cpp">path_info.cpp</a></code> program is handy for learning how class <code>path</code>
iterators,
observers, composition, decomposition, and query functions work on your system.</p>


<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
      <pre><!-- include file "../example/path_info.cpp" -->#include &lt;iostream&gt;
#include &lt;boost/filesystem.hpp&gt;
using namespace std;
using namespace boost::filesystem;

const char * say_what(bool b) { return b ? &quot;true&quot; : &quot;false&quot;; }

int main(int argc, char* argv[])
{
  if (argc &lt; 2)
  {
    cout &lt;&lt; &quot;Usage: path_info path-element [path-element...]\n&quot;
            &quot;Composes a path via operator/= from one or more path-element arguments\n&quot;
            &quot;Example: path_info foo/bar baz\n&quot;
#            ifdef BOOST_POSIX_API
            &quot;         would report info about the composed path foo/bar/baz\n&quot;;
#            else  // BOOST_WINDOWS_API
            &quot;         would report info about the composed path foo/bar\\baz\n&quot;;
#            endif
    return 1;
  }

  path p;
  for (; argc &gt; 1; --argc, ++argv)
    p /= argv[1];  // compose path p from the command line arguments

  cout  &lt;&lt;  &quot;\ncomposed path:\n&quot;;
  cout  &lt;&lt;  &quot;  operator&lt;&lt;()---------: &quot; &lt;&lt; p &lt;&lt; &quot;\n&quot;;
  cout  &lt;&lt;  &quot;  make_preferred()-----: &quot; &lt;&lt; p.make_preferred() &lt;&lt; &quot;\n&quot;;

  cout &lt;&lt; &quot;\nelements:\n&quot;;
  for (auto element : p)
    cout &lt;&lt; &quot;  &quot; &lt;&lt; element &lt;&lt; '\n';

  cout  &lt;&lt;  &quot;\nobservers, native format:&quot; &lt;&lt; endl;
# ifdef BOOST_POSIX_API
  cout  &lt;&lt;  &quot;  native()-------------: &quot; &lt;&lt; p.native() &lt;&lt; endl;
  cout  &lt;&lt;  &quot;  c_str()--------------: &quot; &lt;&lt; p.c_str() &lt;&lt; endl;
# else  // BOOST_WINDOWS_API
  wcout &lt;&lt; L&quot;  native()-------------: &quot; &lt;&lt; p.native() &lt;&lt; endl;
  wcout &lt;&lt; L&quot;  c_str()--------------: &quot; &lt;&lt; p.c_str() &lt;&lt; endl;
# endif
  cout  &lt;&lt;  &quot;  string()-------------: &quot; &lt;&lt; p.string() &lt;&lt; endl;
  wcout &lt;&lt; L&quot;  wstring()------------: &quot; &lt;&lt; p.wstring() &lt;&lt; endl;

  cout  &lt;&lt;  &quot;\nobservers, generic format:\n&quot;;
  cout  &lt;&lt;  &quot;  generic_string()-----: &quot; &lt;&lt; p.generic_string() &lt;&lt; endl;
  wcout &lt;&lt; L&quot;  generic_wstring()----: &quot; &lt;&lt; p.generic_wstring() &lt;&lt; endl;

  cout  &lt;&lt;  &quot;\ndecomposition:\n&quot;;
  cout  &lt;&lt;  &quot;  root_name()----------: &quot; &lt;&lt; p.root_name() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  root_directory()-----: &quot; &lt;&lt; p.root_directory() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  root_path()----------: &quot; &lt;&lt; p.root_path() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  relative_path()------: &quot; &lt;&lt; p.relative_path() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  parent_path()--------: &quot; &lt;&lt; p.parent_path() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  filename()-----------: &quot; &lt;&lt; p.filename() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  stem()---------------: &quot; &lt;&lt; p.stem() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  extension()----------: &quot; &lt;&lt; p.extension() &lt;&lt; '\n';

  cout  &lt;&lt;  &quot;\nquery:\n&quot;;
  cout  &lt;&lt;  &quot;  empty()--------------: &quot; &lt;&lt; say_what(p.empty()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  is_absolute()--------: &quot; &lt;&lt; say_what(p.is_absolute()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_root_name()------: &quot; &lt;&lt; say_what(p.has_root_name()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_root_directory()-: &quot; &lt;&lt; say_what(p.has_root_directory()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_root_path()------: &quot; &lt;&lt; say_what(p.has_root_path()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_relative_path()--: &quot; &lt;&lt; say_what(p.has_relative_path()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_parent_path()----: &quot; &lt;&lt; say_what(p.has_parent_path()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_filename()-------: &quot; &lt;&lt; say_what(p.has_filename()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_stem()-----------: &quot; &lt;&lt; say_what(p.has_stem()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_extension()------: &quot; &lt;&lt; say_what(p.has_extension()) &lt;&lt; '\n';

  return 0;
}<!-- end include file --></pre>
    </td>
  </tr>
</table>


<p>Run the examples below on your system, and try some different path arguments
as we go along. Here is the invocation we will talk about in detail:</p>

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Ubuntu Linux</b></i></td>
    </tr>
    <tr>
      <td>
      <pre>$ ./path_info /foo bar baa.txt

composed path:
  operator&lt;&lt;()---------: "/foo/bar/baa.txt"
  make_preferred()-----: "/foo/bar/baa.txt"

elements:
  "/"
  "foo"
  "bar"
  "baa.txt"

observers, native format:
  native()-------------: /foo/bar/baa.txt
  c_str()--------------: /foo/bar/baa.txt
  string()-------------: /foo/bar/baa.txt
  wstring()------------: /foo/bar/baa.txt

observers, generic format:
  generic_string()-----: /foo/bar/baa.txt
  generic_wstring()----: /foo/bar/baa.txt

decomposition:
  root_name()----------: ""
  root_directory()-----: "/"
  root_path()----------: "/"
  relative_path()------: "foo/bar/baa.txt"
  parent_path()--------: "/foo/bar"
  filename()-----------: "baa.txt"
  stem()---------------: "baa"
  extension()----------: ".txt"

query:
  empty()--------------: false
  is_absolute()--------: true
  has_root_name()------: false
  has_root_directory()-: true
  has_root_path()------: true
  has_relative_path()--: true
  has_parent_path()----: true
  has_filename()-------: true
  has_stem()-----------: true
  has_extension()------: true</pre>
      </td>
    </tr>
  </table>

  &nbsp;

  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
    <tr>
      <td align="center"><i><b>Microsoft Windows</b></i></td>
    </tr>
    <tr>
    <td>
      <pre>&gt;path_info \foo bar baa.txt

composed path:
operator&lt;&lt;()---------: &quot;\foo\bar\baa.txt&quot;
make_preferred()-----: &quot;\foo\bar\baa.txt&quot;

elements:
  &quot;/&quot;
  &quot;foo&quot;
  &quot;bar&quot;
  &quot;baa.txt&quot;

observers, native format:
native()-------------: \foo\bar\baa.txt
c_str()--------------: \foo\bar\baa.txt
string()-------------: \foo\bar\baa.txt
wstring()------------: \foo\bar\baa.txt

observers, generic format:
generic_string()-----: /foo/bar/baa.txt
generic_wstring()----: /foo/bar/baa.txt

decomposition:
root_name()----------: &quot;&quot;
root_directory()-----: &quot;\&quot;
root_path()----------: &quot;\&quot;
relative_path()------: &quot;foo\bar\baa.txt&quot;
parent_path()--------: &quot;\foo\bar&quot;
filename()-----------: &quot;baa.txt&quot;
stem()---------------: &quot;baa&quot;
extension()----------: &quot;.txt&quot;

query:
empty()--------------: false
is_absolute()--------: false
has_root_name()------: false
has_root_directory()-: true
has_root_path()------: true
has_relative_path()--: true
has_parent_path()----: true
has_filename()-------: true
has_stem()-----------: true
has_extension()------: true</pre>
      </td>
    </tr>
  </table>

<p>We will go through the above code in detail to gain a better
understanding of what is going on.</p>

<p>A common need is to compose a path from its constituent
directories. Class <code>path</code> uses <code>/</code> and <code>/=</code> operators to
append elements. That's a reminder
that these operations append the operating system's preferred directory
separator if needed. The preferred
directory separator is a slash on POSIX-like systems, and a backslash on
Windows-like systems.</p>

<p>That's what this code does before displaying the resulting <code>
path p</code> using the <code>class path</code> stream inserter: </p>


<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
      <pre><!-- include file "../example/path_info.cpp" -->  path p;
  for (; argc &gt; 1; --argc, ++argv)
    p /= argv[1];  // compose path p from the command line arguments

  cout  &lt;&lt;  &quot;\ncomposed path:\n&quot;;
  cout  &lt;&lt;  &quot;  operator&lt;&lt;()---------: &quot; &lt;&lt; p &lt;&lt; &quot;\n&quot;;
  cout  &lt;&lt;  &quot;  make_preferred()-----: &quot; &lt;&lt; p.make_preferred() &lt;&lt; &quot;\n&quot;;</pre>
    </td>
  </tr>
</table>


<p>One abstraction for thinking about a path is as a sequence of elements, where
the elements are directory and file names. To support this abstraction, class
<code>path</code> provides iterators and also <code>begin()</code>
and <code>end()</code> functions.</p>

<p>Here is the code that produced the list of elements in the above output listing:</p>

<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
    <pre>cout &lt;&lt; &quot;\nelements:\n&quot;;
for (auto element : p)
  cout &lt;&lt; &quot; &quot; &lt;&lt; element &lt;&lt; &#39;\n&#39;;</pre>
    </td>
  </tr>
</table>

<p>Let&#39;s look at class path observer functions:</p>


<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
      <pre><!-- include file "../example/path_info.cpp" -->  cout  &lt;&lt;  &quot;\nobservers, native format:&quot; &lt;&lt; endl;
# ifdef BOOST_POSIX_API
  cout  &lt;&lt;  &quot;  native()-------------: &quot; &lt;&lt; p.native() &lt;&lt; endl;
  cout  &lt;&lt;  &quot;  c_str()--------------: &quot; &lt;&lt; p.c_str() &lt;&lt; endl;
# else  // BOOST_WINDOWS_API
  wcout &lt;&lt; L&quot;  native()-------------: &quot; &lt;&lt; p.native() &lt;&lt; endl;
  wcout &lt;&lt; L&quot;  c_str()--------------: &quot; &lt;&lt; p.c_str() &lt;&lt; endl;
# endif
  cout  &lt;&lt;  &quot;  string()-------------: &quot; &lt;&lt; p.string() &lt;&lt; endl;
  wcout &lt;&lt; L&quot;  wstring()------------: &quot; &lt;&lt; p.wstring() &lt;&lt; endl;

  cout  &lt;&lt;  &quot;\nobservers, generic format:\n&quot;;
  cout  &lt;&lt;  &quot;  generic_string()-----: &quot; &lt;&lt; p.generic_string() &lt;&lt; endl;
  wcout &lt;&lt; L&quot;  generic_wstring()----: &quot; &lt;&lt; p.generic_wstring() &lt;&lt; endl;</pre>
    </td>
  </tr>
</table>


<p>Native format observers should be used when interacting with the
operating system or with users; that's what they expect.</p>

<p>Generic format observers should be used when the results need to be
portable and uniform regardless of the operating system.</p>

<p><code>path</code> objects always hold pathnames in the native
format, but otherwise leave them unchanged from their source. The
<a href="reference.html#preferred">preferred()</a> function will convert to the
preferred form, if the native format has several forms. Thus on Windows, it will
convert slashes to backslashes.</p>

<p>Moving on to decomposition:</p>


<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
      <pre><!-- include file "../example/path_info.cpp" -->  cout  &lt;&lt;  &quot;\ndecomposition:\n&quot;;
  cout  &lt;&lt;  &quot;  root_name()----------: &quot; &lt;&lt; p.root_name() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  root_directory()-----: &quot; &lt;&lt; p.root_directory() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  root_path()----------: &quot; &lt;&lt; p.root_path() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  relative_path()------: &quot; &lt;&lt; p.relative_path() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  parent_path()--------: &quot; &lt;&lt; p.parent_path() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  filename()-----------: &quot; &lt;&lt; p.filename() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  stem()---------------: &quot; &lt;&lt; p.stem() &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  extension()----------: &quot; &lt;&lt; p.extension() &lt;&lt; '\n';</pre>
    </td>
  </tr>
</table>


<p>&nbsp;And, finally, query functions:</p>


<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#D7EEFF">
  <tr>
    <td>
      <pre><!-- include file "../example/path_info.cpp" -->  cout  &lt;&lt;  &quot;\nquery:\n&quot;;
  cout  &lt;&lt;  &quot;  empty()--------------: &quot; &lt;&lt; say_what(p.empty()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  is_absolute()--------: &quot; &lt;&lt; say_what(p.is_absolute()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_root_name()------: &quot; &lt;&lt; say_what(p.has_root_name()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_root_directory()-: &quot; &lt;&lt; say_what(p.has_root_directory()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_root_path()------: &quot; &lt;&lt; say_what(p.has_root_path()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_relative_path()--: &quot; &lt;&lt; say_what(p.has_relative_path()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_parent_path()----: &quot; &lt;&lt; say_what(p.has_parent_path()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_filename()-------: &quot; &lt;&lt; say_what(p.has_filename()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_stem()-----------: &quot; &lt;&lt; say_what(p.has_stem()) &lt;&lt; '\n';
  cout  &lt;&lt;  &quot;  has_extension()------: &quot; &lt;&lt; say_what(p.has_extension()) &lt;&lt; '\n';</pre>
    </td>
  </tr>
</table>


<p>These are pretty self-evident, but do note the difference in the
result of <code>is_absolute()</code> between Linux and Windows. Because there is
no root name (i.e. drive specifier or network name), a lone slash (or backslash)
is a relative path on Windows but an absolute path on POSIX-like operating
systems. </p>

  <h2><a name="Error-reporting">Error reporting</a></h2>

  <p>The Boost.Filesystem <code>file_size</code> function, like many of the
  operational functions, has two overloads:</p>

  <blockquote>
  <pre>uintmax_t <a name="file_size">file_size</a>(const path&amp; p);
uintmax_t <a name="file_size2">file_size</a>(const path&amp; p, system::error_code&amp; ec);</pre>
</blockquote>
<p>The only significant difference between the two is how they report errors.</p>
<p>The
  first signature will throw exceptions to report errors. A <code>
<a href="reference.html#Class-filesystem_error">filesystem_error</a></code> exception will be thrown
on an
  operational error. <code>filesystem_error</code> is derived from <code>std::runtime_error</code>.
It has a
  member function to obtain the <code>
<a href="../../system/doc/reference.html#Class-error_code">error_code</a></code> reported by the source
  of the error. It also has member functions to obtain the path or paths that caused
  the error.</p>

  <blockquote>

  <p><b>Motivation for the second signature:</b> Throwing exceptions on errors was the entire error reporting story for the earliest versions of
  Boost.Filesystem, and indeed throwing exceptions on errors works very well for
  many applications. But user reports trickled in that some code became so
  littered with try and catch blocks as to be unreadable and unmaintainable. In
  some applications I/O errors aren't exceptional, and that's the use case for
  the second signature.</p>

  </blockquote>

  <p>Functions with a <code>system::error_code&amp;</code> argument set that
  argument to report operational error status, and so do not throw exceptions when I/O
  related errors occur. For a full explanation, see
  <a href="reference.html#Error-reporting">Error reporting</a> in the reference
  documentation. </p>

<hr>
<p>&copy; Copyright Beman Dawes 2010, 2015</p>
<p>Distributed under the Boost Software License, Version 1.0. See
<a href="http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a></p>

</body>

</html>
